The present invention relates generally to electro-optical displays of the type in which electrochromic material undergoes reversible color changes upon the application of an electric field. More particularly, the present invention relates to an improved sandwich construction of an electrochromic display.
In commonly assigned, copending U.S. Pat. Application Ser. No. 054,918 filed July 5, 1979 which is a continuation of Ser. No. 871,618 filed Jan. 23, 1978, now abandoned, there are described an electrochromic display including a porous separator and/or a filter separator each of which can contain an electrolyte. A cavity is defined to cancel the cubic expansion of the electrolyte with rising temperature. The filter separator functions to confine the cavity in the remaining portion except for the display area. However, since the filter separator or glass fibre of the like can not provide the function of reflecting light, light reflection efficiency is inevitably reduced so that it prevents the porous separator from functioning as a background for the layer of the electrochromic material.